1. Field of Invention
The present invention relates to a discharge working machine which supplies a work current from a power source to a work electrode and a workpiece.
2. Description of the Prior Art
FIG. 14 shows a schematic representation of a prior art discharge device. This discharge working machine is adapted to supply a discharge work current from a power source PSO through a diode D, a transistor TO and a coaxial cable CC to a work electrode E and a workpiece W.
A power supply device including power source PSO, diode D, and transistor TO is connected to a main body of the discharge working machine including work electrode E and workpiece W, by coaxial cable CC. The coaxial cable CC helps to decrease the inductance between the power supply device and the discharge working machine main body, thereby enhancing working speed.
The above-mentioned conventional discharge working machine has, in the main body thereof, a connection interposed between the workpiece W and work electrode E. Because coaxial cable CC cannot be used in this portion, a single wire SW has been conventionally used as the connection in this portion. In fact, in the connective portion interposed between the work electrode E and workpiece W, nothing but the single wire SW can be used.
A drawback exists in this structure that when a discharge work current flows through the single wire SW, an inductance is generated in the above-mentioned single wire SW. Because of the inductance, the rise time of the discharge work current signal is lengthened, and the peak value of the discharge current is reduced. This deteriorates the working speed of the machine.
In order to increase the working speed, the power supply PSO voltage must be increased, resulting in a larger consumption of electric power.
In addition, as the size of the discharge working machine is increased, the above-mentioned single wire SW must have a greater capacity, and must be enlarged. A larger wire can cause the working speed to decrease even further. Furthermore, the performance of various discharge working machines (i.e., working speed, etc.) will vary depending on the size of the machine, and cannot be expected to be constant.